全文获取类型
收费全文 | 1852篇 |
免费 | 18篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 7篇 |
综合类 | 9篇 |
化学工业 | 70篇 |
金属工艺 | 16篇 |
机械仪表 | 8篇 |
建筑科学 | 17篇 |
矿业工程 | 2篇 |
能源动力 | 11篇 |
轻工业 | 49篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 31篇 |
一般工业技术 | 28篇 |
冶金工业 | 1503篇 |
原子能技术 | 9篇 |
自动化技术 | 110篇 |
出版年
2021年 | 8篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 13篇 |
2016年 | 8篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 25篇 |
2012年 | 19篇 |
2011年 | 26篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 15篇 |
2007年 | 20篇 |
2006年 | 7篇 |
2005年 | 50篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 45篇 |
1998年 | 421篇 |
1997年 | 263篇 |
1996年 | 165篇 |
1995年 | 89篇 |
1994年 | 85篇 |
1993年 | 83篇 |
1992年 | 15篇 |
1991年 | 19篇 |
1990年 | 17篇 |
1989年 | 23篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 40篇 |
1976年 | 103篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 2篇 |
1970年 | 4篇 |
1968年 | 4篇 |
1966年 | 2篇 |
排序方式: 共有1878条查询结果,搜索用时 15 毫秒
41.
Organic vapor analysis with microsensor arrays relies principally on two output parameters: the response pattern, which provides qualitative information, and the response sensitivity, which determines the limit of detection (LOD). The latter is used to define the operating limit in the low-concentration range, under the implicit assumption that, if a vapor can be detected, it can be identified and differentiated from other vapors on the basis of its response pattern. In this study, the performance of an array of four polymer-coated surface acoustic wave vapor sensors was explored using calibrated response data from 16 solvent vapors in Monte Carlo simulations coupled with pattern recognition analysis. The statistical modeling revealed that the ability to recognize a vapor from its response pattern decreases with decreasing vapor concentration, as expected, but also that the concentration at which errors in vapor recognition become excessive is well above the calculated LOD in most cases, despite the LOD being based on the least sensitive sensor in the array. These results suggest the adoption of a limit of recognition (LOR), defined as the concentration below which a vapor can no longer be reliably recognized from its response pattern, as an additional criterion for evaluating the performance of multisensor arrays. A generalized method for estimating the LOR is presented, as well as a means for improving the LOR via residual error analysis. 相似文献
42.
43.
Jonathan Byrne Erik Hemberg Michael O’Neill Anthony Brabazon 《Genetic Programming and Evolvable Machines》2013,14(3):287-314
A designer should be able to express their intentions with a design tool. This work describes a methodology that enables the architect to directly interact with the encoding of designs they find aesthetically pleasing. Broadening interaction beyond simple evaluation increases the amount of feedback and bias a user can apply to the search. Increased feedback will have the effect of directing the algorithm to more fruitful areas of the search space. We conduct trials on two interfaces for making localised changes to a design in order to evaluate if the user is capable of directing search. In addition, an examination of the locality of changes made by the users provides an insight into how they explore the search space. The results show that a suitably designed interface is capable of directing search and that the participants used different magnitudes of change during directed search. 相似文献
44.
45.
46.
O’Neill M. Saggar S. Richards K. G. Luo J. Singh B. P. Mehra P. Forrestal P. J. 《Nutrient Cycling in Agroecosystems》2021,121(2-3):129-147
Nutrient Cycling in Agroecosystems - We quantified nitrous oxide emission factors (N2O EFs) for cattle urine patches established using two simulation methods: (1) a uniformly wetted area (UWA) and... 相似文献
47.
HP Volz R Rzanny S Riehemann S May H Hegewald B Preussler G Hübner WA Kaiser H Sauer 《Canadian Metallurgical Quarterly》1998,248(6):289-295
Most research with 31P-magnetic resonance spectroscopy (31P-MRS) in affective disorders has been done in the field of bipolar disturbances. Reduced frontal and temporal lobe phosphomonoester (PME) concentrations were measured in the euthymic state, whereas increased values were found in the depressed state. In bipolar-II patients reduced phosphocreatine (PCr) concentrations were reported in the euthymic, depressed, and manic state. The aim of the present study was to explore whether PME and PCr were also altered in the frontal lobe of major depressed, unipolar patients. Therefore, we used 31P-MRS to investigate the relative phospholipid and high-energy phosphate concentrations in the frontal lobe of 14 unipolar patients, mostly medicated, and 8 age-matched controls. We found increased PME and decreased ATP values. Other 31P-MRS parameters were not different in both groups. Phosphomonoester percentages correlated negatively with the degree of depression. Thus, the main alterations found in bipolar depressed patients could also be demonstrated in unipolar depressed patients. The results are discussed with regard to disturbed phospholipid and intracellular high-energy phosphate metabolism in depressed patients. 相似文献
48.
C Robinson SJ Brookes J Kirkham WA Bonass RC Shore 《Canadian Metallurgical Quarterly》1996,10(2):173-9; discussion 179-80
Amelogenin-mineral interactions were investigated using an in vitro binding approach. Rat incisor enamel matrix proteins (mainly amelogenins) were dissolved in synthetic enamel fluid and allowed to equilibrate with deproteinised developing enamel crystals. The results showed that amlogenin proteins of 21, 23, 24, 26 and 27-kDa (corresponding to nascent and partially degraded amelogenins) were associated with the crystals whilst the lower Mr amelogenins (< 21 KDa) remained free in the synthetic enamel fluid. These data suggest the nascent and partially degraded amelogenins may interact with developing enamel crystals and could influence their growth. Albumin-mineral interactions were investigated by extracting developing rat incisor enamel with synthetic enamel fluid. Insoluble material (including the enamel crystals) was then further extracted with 0.1 M phosphate buffer (pH 7.4) to desorb any mineral bound proteins. Western blotting using anti-albumin antibodies showed that almost all of the albumin from the secretory stage enamel and a significant proportion of the albumin present in early transition stage was extractable in the synthetic enamel fluid. However, synthetic enamel fluid did not extract albumin from late transition or maturation stage tissue, which could only be removed following further extraction with phosphate buffer. Albumin degradation was apparent during the transition and maturation stages, where it is degraded and ultimately removed. This binding pattern may be related to amelogenin degradation and removal during the transition stage, permitting albumin access to the previously obscured crystal surfaces. That the secretory stage matrix appears to "protect" secretory stage crystals from albumin may be an important consideration in the aetiology of enamel hypoplasias (i.e. incomplete crystal growth) and when using dissociative extraction procedures for the identification of mineral bound proteins. 相似文献
49.
R Kraus B Reichl SD Kimball M Grabner BJ Murphy WA Catterall J Striessnig 《Canadian Metallurgical Quarterly》1996,271(33):20113-20118
To identify the binding domain for diltiazem-like Ca2+ antagonists on L-type Ca2+ channel alpha1 subunits we synthesized the benzazepine [3H]benziazem as a novel photoaffinity probe. [3H]Benziazem reversibly labeled the benzothiazepine (BTZ)-binding domain of partially purified skeletal muscle Ca2+ channels with high affinity (Kd = 12 nM) and photoincorporated into its binding domain with high yield (>66%). Antibody mapping of proteolytic labeled fragments revealed specific labeling of regions associated with transmembrane segments S6 in repeats III and IV. More than 50% of the labeling was found in the tryptic fragment alanine 1023-lysine 1077 containing IIIS6 together with extracellular and intracellular amino acid residues. The remaining labeling was identified in a second site comprising segment S6 in repeat IV and adjacent residues. Unlike for dihydropyridines, no labeling was observed in the connecting IIIS5-IIIS6 linker. The [3H]benziazem photolabeled regions must be in close contact to the drug molecule when bound to the channel. We propose that the determinants for high affinity BTZ binding are located within or in close proximity to segments IIIS6 and/or IVS6. Therefore the binding domain for BTZs, like for the other main classes of Ca2+ antagonists, must be located in close proximity to pore-forming regions of the channel. 相似文献
50.
C Ferreira-do-Vale A Renzi GP Camargo WA Saad AC Luiz JV Menani JE Silveira LA Camargo 《Canadian Metallurgical Quarterly》1995,28(10):1097-1101
We determined the effects of two classical angiotensin II (ANG II) antagonists, [Sar1, Ala8]-ANG II and [Sar1, Thr8]-ANG II, and losartan (a nonpeptide and selective antagonist for the AT1 angiotensin receptors) on diuresis, natriuresis, kaliuresis and arterial blood pressure induced by ANG II administration into the median preoptic nucleus (MnPO) of male Holtzman rats weighing 250-300 g. Urine was collected in rats submitted to a water load (5% body weight) 1 h later. The volume of the drug solutions injected was 0.5 microliters over 10-15 s. Pre-treatment with [Sar1, Ala8]-ANG II (12 rats) and [Sar1, Thr8]-ANG II (9 rats), at the dose of 60 ng reduced (13.7 +/- 1.0 vs 11.0 +/0 1.0 and 10.7 +/0 1.2, respectively), whereas losartan (14 rats) at the dose of 160 ng totally blocked (13.7 +/- 1.0 vs 7.6 +/- 1.5) the urine excretion induced by injection o 12 ng of ANG II (14 rats). [Sar1, Ala8]-ANG II impaired Na+ excretion (193 +/- 16 vs 120 +/- 19), whereas [Sar1, Thr8]-ANG II and losartan block Na+ excretion (193 +/- 16 vs 77 +/- 15 and 100 +/- 12, respectively) induced by ANG II. Similar effects induced by ANG II on K+ excretion were observed with [Sar1, Ala8]-ANG II, [Sar1, Thr8]- ANG II, and losartan pretreatment (133 +/- 18 vs 108 +/- 11, 80 +/- 12, and 82 +/- 15, respectively). The same doses as above of [Sar1, Ala8]-ANG II (8 rats), [Sar1, Thr8]-ANG II (8 rats), and losartan (9 rats) blocked the increase in the arterial blood pressure induced by 12 ng of ANG II (12 rats) (32 +/- 4 vs 4 +/- 2, 3.5 +/- 1, and 2 +/- 1, respectively. The results indicate that the AT1 receptor subtype participates in the increases of diuresis, natriuresis, kaliuresis and arterial blood pressure induced by the administration of ANG II into the MnPO. 相似文献